Method for transporting a tail end in a fiber web machine from one structural section to another, and also an apparatus and the use of it

ABSTRACT

The invention relates to a method and to an apparatus for transporting a tail end ( 6 ) in a fiber web machine from one structural section to another in such a way that the apparatus comprises nozzles ( 8 ) for guiding the tail end ( 6 ) on the guide plate by means of an air flow ( 4 ). What is essential in the invention is that the blown air ( 2 ) is brought onto a guide plate ( 1 ) shaped into a curve in such a way that the air flow ( 4 ) of the blown air ( 2 ) guides the tail end ( 6 ) onto the curved guide plate ( 1 ) by means of a bump ( 3 ) functioning as an aerodynamic profile, i.e. a bulge guiding the air flow ( 4 ), formed in the curved guide plate ( 1 ). In addition, the invention relates to a use of a curved plate ( 1 ) for transporting a tail end ( 6 ) in a fiber web machine from one structural section to another.

The object of the invention is a method as defined in the preamble of claim 1 for transporting a tail end in a fiber web machine from one structural section to another in such a way that it is guided from the transfer plates by means of an air flow. The invention also relates to an apparatus according to claim 10 and to the use of it as defined in claim 19.

Various solutions are known in the art that are aimed at improving the transfer of a tail end from one structural section to another. Web feeding in fiber web machines, such as in paper machines and board machines, is to an increasing extent air-assisted. They are safe and generally also operationally reliable, as well as being inexpensive to build and use. Solutions known in the art have had a number of drawbacks, e.g. an advantageous airflow speed has not been achieved to the transfer plates. In this respect, the efficiency of apparatus today has not essentially improved. The state-of-the-art is described in applications FI20145349, FI20060757 and also in patents FI 123352 an FI 122377.

It is an object of the present invention to provide a new type of solution for managing web threading in the different parts of the machine, and for different speeds and grades. The solution now utilizes airflow theory more efficiently and at the same time the operation of the apparatus is optimized; the airflow of the blown air can now be directed more accurately at the guide plate. By means of the invention, an even curtain of air can be formed on the guide plate without friction.

More precisely specified, the invention is characterized by what is stated in the claims.

In the following, the invention will be described in more detail with reference to the attached drawings, wherein:

FIGS. 1-10 present a simplified apparatus for transferring a tail end from one structural section to another and also basic diagrams of various possible embodiments of the solution according to the invention.

According to FIGS. 1A-1D, in the invention the airflow 4 of blown air 2 is brought to the surface of the guide plate by means of the special shape of the guide plate. A bump 3 guiding the airflow is shaped in the guide plate 1. This means a curved protrusion that is shaped in the guide plate 1 in such a way that, as viewed from the side, the bump 3 makes a controlled wave-shaped bulge compared to a straight plate. The guide plate 1 is fabricated from metal, plastic, carbon fiber or a corresponding composite. It is generally known in the art to use guide plates that are straight in the longitudinal direction, onto which the blown air is directed. According to FIG. 1D, in the invention the use of a curved guide plate 1 is essential for transporting the tail end 6 in a fiber web machine from one structural section to another in such a way that the tail end 6 is guided on a guide plate by means of an air flow 4.

Broadly interpreting the state-of-the-art, as an illustrative concept the solution can be generally compared to the functioning of the top part of an airplane wing. The aerodynamic profile of the bump 3 guides the air flow 4 of the blown air 2. From the standpoint of the invention, however, what is essential is the technical solution with which the air flow 4 of the blown air 2 can be guided onto the surface of the guide plate 1 and how the air flow 4 is controlled in its entirety.

The purpose of the invention is that the air flow 4 of the blown air 2 is guided along the streamlined surface 5 of the bump 3 functioning as an aerodynamic profile. The air flow 4 of the blown air 2 follows the shape of the surface 5 of the bump 3 and keeps the airflow 4 under the control of the surface 5. In other words, the air flow 4 of the blown air 2 is made to cling to the surface of the bump 3 and to follow it by means of the curved guide plate 1. In this way, the air flow 4 of the blown air 2 adheres to the surface 5 and the tail end 6 can be guided in the direction of the curved guide plate 1.

According to FIGS. 1B and 1C, the aerodynamic bump 3 of the curved guide plate 1 is most preferably formed to start very close to the point from which the blown air 2 is brought to the surface of the guide plate 1, even in such a way that the air flow 4 leaves to immediately follow in a streamlined manner the shape of the surface 5 of the bump 3. Another alternative is presented in FIG. 1A, in which the air flow 4 of the blown air 2 passes first on a straight part 7 formed in the guide plate 1, after which the aerodynamic bump 3 starts. An alternative solution could also be that, instead of a straight section 7, before the aerodynamic bump 3 a step smaller than the bulge could be formed, as a surface curving upwards, or otherwise a recess, as a surface curving downwards.

According to FIG. 4A, in the invention the blown air 2 can be guided onto the surface of the curved guide plate 1 either fully in the direction of the travel direction of the guide plate 1, i.e. without any angle α=0°. Alternatively, according to FIG. 4B, by modifying the shape of the bump 3 of the curved guide plate 1, the blown air 2 can be guided onto the surface of the guide plate 1, or into the proximity of it, either at a negative angle −α, i.e. the blown air 2 is guided towards the surface 5 of the bump 3 formed in the guide plate 1, or at a positive angle +α according to FIG. 4C, at which the blown air 2 is guided upwards from and/or away from the surface 5.

From the standpoint of the invention, completely new opportunities are created in particular by the possibility of guiding the blown air 2 onto the surface of the curved guide plate 1 at a negative angle −α, i.e. the airflow 4 of the blown air 2 is made to collide with the surface 5 of the bump 3 at the desired point. With this arranged collision, it is possible to modify the spreading of the air being blown onto the surface of the guide plate 1 in exactly the manner desired and to guide it onwards onto the tail end 6. Most typically, this brings about a more even distribution of the force pulling the tail end 6, such as a paper tail, i.e. the force is not so point-formed.

From the standpoint of the invention, the aforementioned angle +/−α between the blown air 2 and guide plate 1 is −50°-+5° degrees; it can vary greatly depending on the different operating sites. In principle, even a +20° positive angle could be used, although certainly in practice from the standpoint of the invention the most favorable angle +/−α is in the range −15°-+5° and the optimum angle −5°-+5°. By way of illustration, FIGS. 2A-2C present the extreme embodiments −50° and +20° as well as embodiment examples of a more applicable −15° angle. For this reason, it is essential to factor in that the shape of the curved guide plate 1 can vary very much indeed. The shape of the curved guide plate 1 has been developed on the basis of technical calculations and the combined data of practical test runs. The curved shape is modified and fine-tuned, so that the shape would produce in the flowing air a fairly similar phenomenon to what happens on an airplane wing. It is completely obvious to the person skilled in the art, however, that neither the shape nor the structure of an aircraft wing can be utilized in the solution according to the invention, because what is involved is a completely different intended use, and the technical conditions are in no way comparable.

A solution is sought in the invention for the shape of the guide plate 1 for transporting a tail end 6 in a fiber web machine. It is important for the invention that the air flow 4 strongly follows the shape of the curve, very close to the surface 5 of the curve, without appreciably trying to disperse away from the surface of the curve. This is an important advantage, because in a flat tail end the air mattress tries to become thicker on the surface of the plate as a function of the distance from the blowing nozzle. The curved shape of the guide plate 1 minimizes this effect and keeps the air mattress thin. This considerably improves the control of the tail 6 in threading and enables the use of smaller air volumes, which in turn improves the energy efficiency of this solution. Important observations were made in test runs, and by means of technical solutions the shape of the curved guide plate 1 was optimized in such a way that the air flow 4 of the blown air 2 follows the streamlined shape of the surface 5 of the bump 3 functioning as an aerodynamic profile and keeps the airflow 4 under the control of the surface 5.

Owing to what is presented above, the shape of the curved guide plate 1 is difficult to specify on the basis of just the dimensions; more particularly, an unambiguous mathematical definition of the shape of the curve is difficult. This is made more difficult, also, because the curved shape of the guide plate 1 varies depending on the application. That being the case, the shape of both the bump 3 and of the surface 5 of the curved guide plate 1, and the length L, height H and angle β of the curve, as well as the radius R are dimensioned on a case-by-case basis in the manner required by different applications, and are finally tailored on-site to be optimal. FIG. 5A presents by way of example the shape of both the bump 3 and the surface 5 of a curved guide plate 1, wherein the length L of the bump 3 is in the range 20-300 mm, depending on the length of the threading guide plate 1 and the distance from the tail end 6 to be transferred. The most suitable length is 50-150 mm, in this exemplary embodiment L=75 mm. More precisely specified, L is the length from the discharge aperture to the highest point of the bump 3 from the nozzle 8.

The height H of the bump 3 means the difference of the nozzle 8 of the discharge aperture and the surface 5 of the bump 3. What is essential is the difference of the surface 5 in relation to the nozzle 8 of the discharge aperture, i.e. that it is situated at some desired height H. In other words, depending on the point at which the nozzles 8 of the discharge apertures are situated, the nozzles 8 can be higher, lower or at the same height with respect to the surface 5; this dimension is defined as the height H. In the exemplary embodiment, the height H of the bump 3 from the plane surface is 0.1-50 mm, most preferably 2-10 mm, in this exemplary embodiment H=6 mm.

The angle β between the blown air 2 and the surface of the guide plate 1 after the bump 3 is selected freely according to the different points. More precisely specified, the angle β is the contact angle or rounding of the bump 3 and the curved guide plate 1. In this exemplary embodiment, β=13°, in other words, the angle β between the blown air 2 and the surface of the guide plate 1 after the bump 3 is positive, i.e. bends in a slope downwards, the angle is +β. Another alternative is the embodiment according to FIG. 5B, in which the flat section of the surface of the guide plate 1 is formed into an upward slope in relation to the bump 3, the angle is −β, i.e. negative.

In the embodiment of FIG. 5A, the radius R₁ of the bump 3 is in the range 10-500 mm, most suitably 100-300 mm, in this exemplary embodiment R₁=199 mm, and the radius R₂ is in the range 20-400 mm, most suitably 50-200 mm, in this exemplary embodiment R₂=166 mm. Defined more precisely, if the bump 3 is of a circular type, R₁ is the radius of the bump 3. R₂ is the radius of the countercircle, with which the bump 3 is connected to the flat section. The shape of the bump 3 can vary according to need; it can be a slope from the entry side of the air flow 4 and a double curve curving to the surface of the flat guide plate 1. According to FIG. 5C, R₁ can also be composed of two or more different-sized circles, e.g. a gentle curve R_(1.1) after the air blowing 2, and a tightening curve R_(1.2) at the highest point of the bump 3, and a further tightening curve R_(1.3) towards the flat plate of the guide plate 1.

In addition to this, the nozzles 8 of the air discharge apertures of the blown air 2 can be formed in a number of ways. According to one embodiment of the invention, the quantity of nozzles 8 required by the usage location are installed at different points of the curved guide plate 1. FIG. 6A presents a curved guide plate 1 having a width A=390 mm and in which the nozzles 8 of the air discharge apertures are at a distance B=35 mm from the side end of the plate with a distribution of C=20 mm in such a way that the width covered by the nozzles 8 is D=320 mm.

Furthermore, the nozzles 8 can blow at different angles +/−α onto the surface of the curved guide plate 1, depending on the type of nozzle 8 and on the task. According to one embodiment of the invention, some of the nozzles 8 are pull nozzles, in other words the maximum tension force is sought, and some are hold nozzles with which controllability is managed. FIGS. 10A and 10B describe a steep and a slope-type step nozzle that have a step and are suitable as hold nozzles in the solution according to the invention. These differ substantially from the even pull nozzles according to FIG. 10C that have no step. With a suitable combination of these, the passage of the tail end 6 is optimized.

One preferred embodiment is the solution according to FIG. 6B, in which is e.g. a 3 m long plate and in which there are nozzles 8, at 300 mm intervals. Some of the nozzles 8 are hold nozzles and some are even pull nozzles that guide towards the bump 3 for guiding the tail end 6. The surface of the curved guide plate 1 after the bump 3 is shaped according to the different operational needs; it can be an essentially even and straight plane, curved, or the next bump 3 starts from it. In this way, one larger entity is formed that here we call a guidance system. According to FIGS. 8A-8C, this type of guidance system can curve as desired, e.g. evenly for the whole distance, or it can be straight for some of the distance and then coil e.g. around a roll for some distance. According to FIGS. 9A-9C, the guidance system can be made from one integral guide plate 1, in which same plate a number of bumps 3 are formed. There can be a hinge structure in the guide plate 1, or it can be made from a thinner or flexible plate so that it can coil. Most preferably, the guidance system is made from parts, from a number of guide plates 1, which are fastened to each other in such a way that a plurality of curved guide plates 1 are connected into one larger web feeding guidance system. The guide plates 1 are fastened to each other from more than one plate, the plates being either similar or different, most preferably from 2-10 curved guide plates 1. In this way, the desired guide plate entity, i.e. guidance system, is formed, which guides the tail end 6 either straight and/or curving in the desired manner, and that the guidance system comprises various nozzles 8 and also bumps 3.

According to FIGS. 3A-3B, the section of the guide plate 1 starting after the surface 5 of the curved guide plate 1 can, according to a particularly preferred embodiment, continue both curving 11 and straight 10. In other words, 10 mm battens or narrow grooves, i.e. longitudinal gaps of different sizes, are cut from the plate, of which most preferably every alternate gap continues straight and every other alternate gap bends downwards as an extension of the curved part. In this way, some of the blown air 2 can be ejected through the flat part 10 and thus the tail end 6 can be brought under control, on top of the battens that continue straight, and into contact with the curved surface 11. The grooves in the embodiment of FIG. 3A go to the end of the guide plate 1 and in FIG. 3B they are formed in only a part of the guide plate 1. What is essential, however, is that the purpose of the batten is not to go through the bump 3, but instead to start after the bump 3. This embodiment is advantageous in precise situations, e.g. through a roll nip, in which the tail end 6 must be transported through a small gap and it should be as straight and even as possible.

According to what is presented in the preceding, from the standpoint of the invention an essential embodiment is when the blown air 2 can be guided onto the surface 5 of the curved guide plate 1 without any shoulder or angle α (0°), and without producing any friction. This way, the maximum tension force is achieved. With solutions according to the state-of-the-art this is impossible; there is always a blowing angle between the guide plate and the bores of the nozzles. It is technically impossible to bore holes in the nozzles in exactly the same direction as the surface of a flat plate. For example, in specification FI 123352, in which the angle between the blowing direction of the bores and the guide plate must be between +5°-+30° degrees. Essential improvements are achieved with the solution according to the invention compared to the prior art presented above, in which the air discharges through the plates at a small angle to the bored holes.

The invention can also be applied in two ways; either in such a way that the nozzles 8 of the air discharge apertures of the blown air 2 are prefabricated in the curved guide plate 1. This type of nozzle structure 8, which is made as a fixed part of the curved guide plate 1, is suited according to FIG. 7B in particular in threading in the drying section of a paper machine, in which the blowing is in two directions.

Another very important embodiment is presented in FIG. 7A in such a way that the nozzles 8 are made in a separate profile, i.e. into a separate nozzle frame 9, onto which the curved guide plate 1 is installed. This type of nozzle frame 9 is fabricated from a separate profile, in which nozzles 8 are formed in such a way that the nozzle structure 8 can be stepped, angled or planar, and the guide plate 1 is installed with fastening means 12 onto the nozzle frame 9, forming an integral entity. These different variations can, of course, be varied according to need. This type of replaceable nozzle frame 9-guide plate 1 combination is an extremely good solution from the standpoint of the invention; in such a case, the threading event can be adjusted/optimized in situ by changing the nozzle structure 8 and/or guide plate profile.

It is obvious to the person skilled in the art that the invention is not limited to the embodiments presented above, but that it can be varied within the scope of the claims presented below. 

1. Method for transporting a tail end (6) in a fiber web machine from one structural section to another in such a way that the tail end (6) is guided on a guide plate (1) by means of an air flow (4), characterized in that in the method blown air (2) is brought onto a guide plate (1) shaped into a curve in such a way that the air flow (4) of the blown air (2) guides the tail end (6) onto the curved guide plate (1) by means of a bump (3) functioning as an aerodynamic profile, i.e. a bulge guiding the air flow (4), formed in the curved guide plate (1) in such a way that the air flow (4) follows the curved guide plate (1) and guides the tail end (6) in a direction parallel to its travel direction.
 2. Method according to claim 1, characterized in that the air flow (4) guiding the tail end (6) follows along the streamlined surface (5) of the bump (3) functioning as an aerodynamic profile, keeping the air flow (4) in the control of the surface (5) in such a way that the air flow (4) follows mainly, most preferably in its entirety, the curved guide plate (1) and simultaneously guides the tail end (6) in a direction parallel with the guide plate (1).
 3. Method according to claim 1 or 2, characterized in that the shape of the side profile of the bulge guiding the air flow (4), i.e. the bump (3) functioning as an aerodynamic profile, is, at its simplest, semicircular or convex, the shape, size, radius of which, as well as both the angle of incidence and the flow-off angle, are the same in the upstream direction and downstream direction of the blown air (2), or most preferably the bump (3) is asymmetrical, the shape, size, radius of which, as well as both the angle of incidence and the flow-off angle, are different in the upstream direction and downstream direction of the blown air (2).
 4. Method according to claim 1-3, characterized in that the height H is the difference of the nozzle (8) of the discharge aperture and the surface (5) of the bump (3) functioning as an aerodynamic profile, in such a way that the height (H) of the bump (3) from the plane surface of the guide plate (1) is 0.1-50 mm, most preferably 2-10 mm, the length is L 20-300 mm, most preferably 50-150 mm, and the radius R₁ of the bump (3) is in the range 10-500 mm, most suitably 100-300 mm, and the radius R₂ to the plane surface of the guide plate (1) is in the range 20-400 mm, most suitably 50-200 mm in such a way that the blown air (2) follows the shape of the bump (3) close to the surface (5) keeping the air mattress thin without trying to disperse it away from the surface (5).
 5. Method according to claim 1-4, characterized in that the blown air (2) is guided onto the surface of the curved guide plate (1), or into the proximity of it, at an angle α, which is in the range of −50°-+5°, a favorable angle α being most preferably in the range −15°-+5° and the optimum angle α being in the range −5°-+5°, including guidance of the blown air (2) at the angle α=0° fully in the direction of the travel direction of the curved guide plate (1), and in that the angle between the blown air (2) and the plane surface of the guide plate (1) after the bump (3), which is the contact angle or rounding of the bump (3) and the curved guide plate (1), is +/−β in such a way that a positive angle +β is formed sloping downwards and that a negative angle −β is formed sloping upwards.
 6. Method according to claim 1-5, characterized in that the aerodynamic bump (3) of the curved guide plate (1) is most preferably formed to start very close to the point from which the blown air (2) is brought to the surface of the guide plate (1), even in such a way that the air flow (4) leaves to immediately follow in a streamlined manner the shape of the surface (5) of the bump (3), alternatively the air flow (4) of the blown air (2) passes first on a straight part (7) formed in the guide plate (1), after which the aerodynamic bump (3) starts.
 7. Method according to claim 1-6, characterized in that battens or narrow pieces (10, 11) are formed in the curved guide plate (1) in such a way that starting at the aerodynamic bump (3) or after it, a part of the curved guide plate (1) continues curved (11) and a part straight (10), most preferably in such a way that every alternate piece continues straight (10) and every other alternate piece bends in a curve (11).
 8. Method according to claim 1-7, characterized in that the nozzles (8) of the air discharge apertures of the blown air (2) are prefabricated in the curved guide plate (1), or in that the nozzles (8) are made in a separate and replaceable nozzle frame (9) in such a way that the nozzle structure is stepped, angled or planar and the curved guide plate (1) is installed with fastening means (12) onto the nozzle frame (9) forming an integral entity.
 9. Method according to claim 1-8, characterized in that a plurality of curved guide plates (1) are connected into a larger web feeding guidance system in such a way that the guide plates (1) are fastened to each other from more than one plate, most preferably from 2-10 curved guide plates (1), or alternatively the plate is formed from one piece, forming the desired guide plate entity that guides the tail end (6) either straight and/or curves in the desired manner, and in that the guidance system comprises various nozzles (8) and also bumps (3).
 10. Apparatus for transporting a tail end (6) in a fiber web machine from one structural section to another in such a way that the apparatus comprises nozzles (8) for guiding the tail end (6) on the guide plate by means of an air flow (4), characterized in that in the apparatus the guide plate (1), onto which the blown air (2) is brought, is shaped to be curved a bump (3) functioning as an aerodynamic profile is formed in the curved guide plate (1), which bump is shaped in such a way that the bump (3) forms a bulge guiding the air flow (4), nozzles (8) are installed to structurally direct the blown air (2) in such a way that the air flow (4) follows the curved guide plate (1) and guides the tail end (6) in a controlled fashion in a direction parallel to its travel direction.
 11. Apparatus according to claim 10, characterized in that the bulge of the bump (3) functioning as an aerodynamic profile is shaped to be a streamlined surface (5) that keeps the air flow (4) in the control of the surface (5) in such a way that the air flow (4) follows mainly, most preferably in its entirety, the curved guide plate (1) and simultaneously guides the tail end (6) in a direction parallel with the guide plate (1).
 12. Apparatus according to claim 10 or 11, characterized in that the shape of the side profile of the bump (3), of the bulge guiding the air flow (4), is at its simplest, semicircular or convex, the shape, size, radius of which, as well as both the angle of incidence and the flow-off angle, are the same in the upstream direction and downstream direction of the blown air (2), or most preferably the bump (3) is asymmetrical, the aerodynamic shape, size, radius of which, as well as both the angle of incidence and the flow-off angle, are different in the upstream direction and downstream direction of the blown air (2).
 13. Apparatus according to claim 11-12, characterized in that the height H is the difference of the nozzle (8) of the discharge aperture and the surface (5) of the bump (3) functioning as an aerodynamic profile in such a way that the height (H) of the bump (3) from the plane surface of the guide plate (1) is 0.1-50 mm, most preferably 2-10 mm, the length is L 20-300 mm, most preferably 50-150 mm, and the radius R₁ of the bump (3) is in the range 10-500 mm, most suitably 100-300 mm, and the radius R₂ to the plane surface of the guide plate (1) is in the range 20-400 mm, most suitably 50-200 mm.
 14. Apparatus according to claim 10-13, characterized in that the nozzles (8) are installed to structurally direct the blown air (2) onto the surface of the curved guide plate (1), or into the proximity of it, at an angle α, which is in the range of −50°-+5°, a favorable angle α being most preferably in the range −15°-+5° and the optimum angle α being in the range −5°-+5°, including guidance of the blown air (2) at the angle α=0° fully in the direction of the travel direction of the curved guide plate (1), and in that the angle between the blown air (2) and the plane surface of the guide plate (1) after the bump (3), which is the contact angle or rounding of the bump (3) and the curved guide plate 1, is +/−β in such a way that the positive angle +β is formed sloping downwards and that the negative angle −β is formed sloping upwards.
 15. Apparatus according to claim 10-14, characterized in that the aerodynamic bump (3) of the curved guide plate (1) is most preferably formed to start very close to the structural point from which the blown air (2) directed by the nozzles (8) is brought to the surface of the guide plate (1), even in such a way that the air flow (4) leaves to immediately follow in a streamlined manner the shape of the surface (5) of the bump (3), or alternatively the air flow (4) of the blown air (2) passes first on a straight part (7) formed in the guide plate (1), after which the aerodynamic bump (3) starts.
 16. Apparatus according to claim 10-15, characterized in that battens or narrow pieces (10, 11) are formed in the curved guide plate (1) in such a way that starting at the aerodynamic bump (3) or after it, a part of the curved guide plate (1) continues curved (11) and a part straight (10), most preferably in such a way that every alternate piece continues straight (10) and every other alternate piece bends in a curve (11).
 17. Apparatus according to claim 10-16, characterized in that the nozzles (8) of the air discharge apertures of the blown air (2) are either preformed in the curved guide plate (1) or in that the nozzles (8) are made in a separate and replaceable nozzle frame (9) in such a way that the nozzle structure is stepped, angled or planar and the curved guide plate (1) is installed with fastening means (12) onto the nozzle frame (9) forming an integral entity.
 18. Apparatus according to claim 10-17, characterized in that a plurality of curved guide plates (1) are connected into a larger web feeding guidance system in such a way that the guide plates (1) are fastened to each other from more than one plate, most preferably from 2-10 curved guide plates (1), or alternatively the plate is formed from one piece, forming the desired guide plate entity, that guides the tail end (6) either straight and/or curves in the desired manner, and in that the guidance system comprises various nozzles (8) and also bumps (3).
 19. Use of a curved guide plate (1) for transporting a tail end (6) in a fiber web machine from one structural section to another in such a way that the tail end (6) is guided on the curved guide plate (1) by means of an air flow (4).
 20. Use according to claim 19 of a bump (3) as an aerodynamic profile on a curved guide plate (1) in such a way that the bump (3) forms a bulge guiding the air flow (4), which bulge is shaped to be a streamlined surface (5) that keeps the air flow (5) in the control of the surface (4) in such a way that the air flow (4) follows mainly, most preferably in its entirety, the curved guide plate (1) and simultaneously guides the tail end (6) in a direction parallel with the guide plate (1).
 21. Use of nozzles (8) according to claim 19-20, which nozzles (8) are installed to structurally direct the blown air (2) in such a way that the air flow (4) follows the curved guide plate (1) and guides the tail end (6) in a controlled fashion in a direction parallel to its travel direction.
 22. Use of a nozzle frame (9) according to claim 19-21 together with a curved guide plate (1). 